Effect of load and sliding velocity on the wear behaviour of infiltrated TiC/Cu–Ni composites

Abstract

Cu–Ni alloys are thermally and chemically operationally stable alloys. Even though its wear resistance is superior to that of its pure metal components, the addition of reinforcing phases can further improve the wear behaviour of the alloys in an attempt to develop lighter materials resistant to degradation by corrosion and wear. The dry sliding wear behaviour of Cu10Ni matrix composites reinforced with 55 vol% TiC particles was investigated in an experimental pin-on-ring arrangement with a AISI M2 hardened steel ring as a counterpart at normal loads of 25 N, 52 N and 103 N, and sliding velocities of 0.3 m/s, 0.6 m/s and 0.8 m/s. The worn surfaces and wear debris were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (SEM-EDS) and x-ray diffraction (XRD) techniques. The infiltrated composites had less than 1.8% porosity. The Cu10Ni alloy exhibited significant material displacement towards the wear track margin and a highly deformed subsurface up to more than 200 μm deep. Despite the higher wear rate of the unreinforced alloy, the coefficient of friction (COF) of Cu10Ni was lower because of the hard-particles exposed in the surface of the composites. The dominant wear mechanism of the alloy was adhesive and oxidative wear. In the least case, the TiC/Cu10Ni composite has three times more wear resistance than the pure Cu10Ni matrix. The wear behaviour of the composite is characterized by a tribochemical reaction that involves oxidation of the matrix and transferred material forming protective tribolayers through an additional sliding process. The surface consists of numerous simple and mixed oxides of Fe, Cu and Ni. The highest rate of composite wear was achieved in the combination of maximum sliding velocity and higher applied load. The mechanism that governs the wear process in composites combines abrasive, adhesive and oxidative wear.